1. Field
This disclosure relates generally to processes for forming semiconductor devices, and more specifically, to processes for forming a semiconductor device having epitaxially grown source and drain regions.
2. Related Art
Traditional methods for forming semiconductor devices having epitaxially grown source and drain regions involve several hydrofluoric acid cleaning steps, such as “HF clean.” For example, taking a p-channel device with epitaxial source/drain regions, as an example, after source/drain recesses are formed, an HF clean process is performed. This step, however, results in a removal of some of the field oxide used as part of isolation regions and the oxide used to mask the n-channel devices. Moreover, subsequent removal of the oxide mask used to mask the n-channel devices using an HF cleaning process results in further removal of field oxide used as part of the isolation regions. This undesirable removal of field oxide can have several deleterious effects. For example, when dual etch-stop layers are formed to generate compressive or tensile strain in the channel regions of the semiconductor device, the loss of field oxide can cause unfavorable stress alignment from the dual etch-stop layers. Furthermore, the loss of field oxide in the isolation regions also can cause lower stress from the isolation regions.
Accordingly, there is a need for processes for forming a semiconductor device having epitaxially grown source and drain regions.